Purification of light mineral oil distillates



Patented Feb. 18, 1941 UNITED STATES PATENT OFFICE Robert E. Burk and Everett 0. Hughes, Cleveland, Ohio, assignors to The Standard Oil Company,

Cleveland, Ohio, a

No Drawing. Application corporation of Ohio August 31, 1938,

Serial No. 227,766

2 Claims.

In treating light mineral oil distillates it is known practice to selectively take out hydrogen sulphide, and separately remove sulphur compounds of different type such as mercaptans. We have now found however that superior advantages may be had by so treating the distillates as to avoid common action on certain other compounds which are prone to be prevalent along with mercaptan sulphur and which otherwise introduce some complication in reaction efficiency.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described, and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative however, of but a few of the various ways in which the principle of the invention may be employed.

The mineral oil distillate which is to be purified, as for example gasoline, kerosene etc., is, in accordance with our invention, freed of hydrogen sulphide if this is not already absent. This may be accomplished in known ways, or preferably in the case of suitably light distillates we pass the distillate through a zone at a sufficient temperature and separating conditions to drive off or distill off the lightest molecules including dissolved hydrocarbons through propane and butane and the hydrogen sulphide, a fractionating operation being involved, such as in a debutanizer. With the distillate practically freed from hydrogen sulphide, we then subject it to the action of a weak caustic soda solution, such as 0.5 to 8 B., at a temperature of 50 to 140 F., and remove certain oxygen-containing acid-acting carbon ring compounds of naphthenic acid type and cresolic type especially. We have found that in this way the succeeding treating solution is surprisingly more effective upon mercaptans and is more easily subsequently regenerated and also separates more cleanly from the distillate after being mixed therewith in the treating operation. The treating solution and the distillate being mixed and separated, the distillate is next subjected to the action of a relatively strong caustic soda solution, as for instance 4 to 20 B., at a. temperature of 50 to 140 F., to remove mercaptans, and. after well mixing and agitating and separating, the caustic solution is subjected to the action of steam, or sulphur added in elemental form in suitable amount as controlled generally by the content of mercaptide; or we may blow an oxygen-providing 5 gasiform agent as steam or oxygen through the solution, preferably elemental sulphur having been added, and it is usually desirable to have a metallic sulphide, as lead sulphide, copper sulphide, or the like, present, in catalytic relation. 10 The caustic solution is returned to treat further quantities of distillate, and the distillate as emerging from the treatment is particularly low in mercaptanic sulphur.

Other modes of applying the principle of the 15 invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims, or the equivalent of such, be employed.

We therefore particularly point out and dis- 20 tinctly claim as our invention:

1. A process of purifying light petroleum distillates, which consists of removing hydrogen sulphide by means that do not remove substantial amounts of oxygen-containing acid-reacting carbon ring compounds and mercaptans. then selectively converting oxygen-containing acid-reacting carbon ring compounds in the distillate to metal-containing compounds and removing the same by subjecting to the action of a dilute caustic soda solution of 0.5 to 8 degrees Baume' without substantially reacting on mercaptans, then acting on mercaptans by a more concentrated caustic soda solution.

2. A process of purifying light petroleum distillates, which consists of providing a distillate free from hydrogen sulphide which contains substantial amounts of oxygen-containing acidcompounds and mercaptans, theln selectively converting oxygen-containing acid-reacting carbon ring compounds in the distillateto metal-containing compounds and removing the same by subjecting to the action of a dilute caustic soda solution of 0.5 to 8 degrees. Baum without substantially reacting on mercaptans, then acting on mercaptans by a more concentrated caustic soda solution.

ROBERT E. BURK.

EVERETT C. HUGHES. 

